The aim of this project is the study of the structural and functional properties of the receptors for glycoprotein hormones (human chorionic gonadotropin, lutropin, follitropin, thyrotropin), tetanus toxin, and interferon. These effectors interact with responsive cells recognizing membrane receptors that are characterized by a unique oligosaccharide chain of a glycoprotein or a glycolipid. Hormones and toxins share important structural similarities sufficient to suggest similar mechanisms of action. The proposed research will emphasize on the role of glycoproteins, glycolipids and phospholipids in the expression of receptor activity of plasma membrane and isolated cells. Continuous cell lines from normal rat thyroid and from several experimental thyroid tumors will be selected for specific and unique alterations in the components of the receptor. These alterations will be correlated not only with the binding properties for a given effector but also with the ability of such effector to cause metabolic changes in the target cell, such as modification of membrane potential, ion transport and of the levels of cyclic nucleotides. Membrane perturbations caused by the effectors will be investigated probing the chemical reactivity of receptor components in the absence and in the presence of the effectors. The conformational changes imposed by soluble receptor components on specific effectors will be monitored by spectroscopic techniques such as fluorescence and circular dichroism.